1. Field of the Invention
The invention relates to a developing device and an image forming apparatus.
2. Description of Related Art
In an image forming apparatus such as a printer, copy machine, facsimile machine, MFP (multifunctional Peripheral), for example, in a printer, a charging roller charges the surface of a photosensitive drum, a LED head emits light to form an electrostatic latent image on the surface of the photosensitive drum, a developing device having a developing roller serving as a developer carrier electrostatically supplies a toner layer serving as a developer layer formed on the developing roller to the surface of the photosensitive drum so as to develop the electrostatic latent image to form a toner image, a transfer roller transfers the toner image onto a medium, and a fixing unit fixes the toner image on the medium so as to form a permanent image on the medium.
In order to supply the toner to the developing roller, there is a belt-type toner supplying device. Such a belt-type toner supplying device includes a drive roller, a driven roller, and a toner supplying belt stretched between the drive roller and the driven roller. A voltage is applied to the drive roller to produce an electric field for supplying toner from the toner supplying belt to the developing roller, and a voltage is applied to the driven roller to produce an electric field for removing toner remaining on the developing roller after the development process (see, for example, Japanese Patent Application Laid-Open No. H6-35381).